Contacting device for high pressure absorption



Feb. 1o, 1942. G. s. BAYS 2,272,503

CONTACTING DEVICE FOR HIGH PRESSURE ABSORPTION Filed April 50, 1940 2 Sheets-Sheet l` @www Feb. 1o, 1942. l G. s. BAYS 2,272,503

CONTACTING DEVICE FOR HIGH PRESSURE ABSORPTION Filed April '.50, 1940 2 Sheets-Sheet 2 60A/74am@ 25 1g MKM Patented Feb. 10, 1,942

ooN'rAoTiNo DEVICE Fon man PRESSURE AnsonPTIoN George S. Bays, Tulsa, kla.assignor to Stanolind-Oil and Gas Company, Tulsa, Okla., a corporation of Delaware Application April 30,

v1 Claim.

'I'his invention relates to apparatus for absorption at elevated pressures and particularly to apparatus for recovering normally liquid hydrocarbons from high pressure riuids produced by wells of the so-called distillate type.

As drilling operations have been carried to greater and greater depths in the search for oil and gas deposits, a large number of wells have been discovered in which the hydrocarbon uids are apparently present in the reservoir at very high pressures, often ranging from 2000 pounds per square inch to'as high as 10,000 pounds per square inch. While some of these reservoirs contain a minor amount of liquid phase hydrocarbons, all or the bulk of the hydrocarbons are usually present in the reservoir in the gas phase although this gas phase contains substantial amounts of normally liquid hydrocarbons. In most instances a distillate reservoir is at a pressure in excess of the critical pressure of the hydrocarbon system present therein, or at least in excess of the critical pressure of the hydrocarbon system produced therefrom, and insuch instances it may be more accurate to speak of the phase condition asa high density super-critical phase which is not distinctly either gas or liquid.

Well fluids produced from distillate reservoirs necessarily encounter a reduction in both pressure and temperature in progressing .up the well and since the reservoir pressure in the case of typical distillate-type reservoirs is in the socalled retrograde condensation range the reduction in pressure as well as the reduction in temperature tends to precipitate liquid hydrocarbons as a distinct liquid phase. However, under the high pressure conditions existing atv the -well head, for instance at least 1200 or 1500 pounds per square inch and more typically 2000 to 5000 pounds per square inch or still higher, the gas or super-critical phase retains a very large part of the normally liquid hydrocarbons present.

Processes have been devised for recovering a large amount of these normally liquid hydrocarbons. Thus, for instance, the well uids can be further cooled after leaving the well and can can then be expanded to some lower pressure within the retrograde condensation range.

The retrograde condensation range is thc range in which the amount of liquid phase increases with decreasing pressure. This effect persists down to some minimum pressure which varies to a considerable extent with the particular hydrocarbon system involved and with the temperature but which is typically in the neighborhood of- 700 to 1000 pounds per square 1940, Serial No. 332,566

inch. Below this pressure which constitutes the base of the retrograde condensation range, further pressure reduction tends to cause liquid hydrocarbons to pass into the gas phase, thus decreasing rather than increasing the yield of total liquids.

For this `reason prior art processes have in many instances limited the pressure reduction to a separator pressure within the retrograde condensation range. In general it has been necessary to lower the pressure to some value not greatly in excess 'of the base of the retrograde condensation range in order to obtain the desired high yields. Thus separator or absorber pressures of 700 to 1200 pounds per square-inch have been typical.

In orderto prevent retrograde vaporization CII within the reservoir and thus increase thev ultimate recovery, as well as for purposes of economy and conservation, it is customary to cycle the gas from which the liquid phase hydrocarbons have been recovered to the sub-surface reservoir from which they were produced or to another sub-surface reservoir. This necessitates recompression and the cost of such recompression increases very rapidly as the pressure oi the distillate recovery operation is reduced. 'I'hus it is extremely desirable to recover the liquid phase hydrocarbons at as high a pressure as possible.

Using the ordinaryl retrograde condensation type of operation, however, the pressure must be reduced tosome value not greatly in excess of 1200 pounds per square inch in order to obtain the desired high yield of normally liquid hydrocarbons.

The amount of such liquid hydrocarbons recovered at a given pressure can be materially increased if a suitable absorption medium is con- 40 tacted with the well liuids. Moreover, the recovery pressure can also be increased while still retaining the advantage of improved recovery. Suitable absorption media include the heavier ends of the distillate recovered, various types of heavy absorption media. suchA as aromatic or naphthenic hydrocarbon fractions boiling pnedominantly above the end pointof the distillate to be recovered and other types of absorber oils.

Such high pressure absorption processes have had, however, serious disadvantages. Due to the high pressures which must be used to secure economical processing, the density difference between the gas and liquid phases present in the absorption step is much less than in ordinary low pressure absorption operations with the result that countercurrent absorption in a bubble tower, packed tower, baiiled tower or the like tends to be very difdcult ii.' not impossible. Such towers tend to foam or puck" and separation is extremely diillcult. Furthermore, these conditions lead to highly inelcient operations in which the advantages ofl countercurrent processing are not obtained to any worthwhile degree.

On the other hand, if the absorption medium and well fluids are contacted in concurrent fashion and then separated by the use of settling chambers, mist extractors or centrifuges, the result is the same as for a batch process or, in other words, the same as for a countercurrent tower of only one theoretical plate.

It is an object of my invention to provide a paratus which makes possible a high pressure absorption process of the type particularly adapted to distillate recovery operations which combines the advantages Ioi both concurrent and countercurrent operations. Another object of my invention is to provide apparatus for recovering distillate hydrocarbons from distillate well fluids at pressures higher than those possible heretofore, with consequent economy in recompression costs. A still further object is to provide a superior contactor Vfor use as described. Other and more detailed objects, advantages and uses of my invention will become apparent as the description thereof proceeds.

I contemplate, in general, taking high pressure fluids from a well of` the distillate type, removing, if so desired, the liquid hydrocarbons formed in the passage of the well iiuids out of the well together, if desired, with such additional liquid hydrocarbons as can be recovered by some moderate reduction of the temperature and/or pressure of the -well uids and then passing the remaining gas or super-critical phase hydrocarbons (or the totallwell fluids, if desired) into a high pressure absorption system operating at a pressure of at least .1200 pounds per square inch andin most instances at a pressure of at .least 1500 pounds per square inch. 'The pressures in the absorption system will be as high as is con,`

sistent with thev desired operation and will depend in large measure on the particular well fiuidswith which one is concerned'and with the particular apparatus available. However, such pressures maybe as high as 3000 or even 4000 pounds per square inch orin some instances still higher.

In this high pressure absorption system the well fluids, or the desired portion of them, are contacted with a suitable absorption medium having a lower volatility or higher average boiling `point thanthat of thedistillate to be re- I covered. This contacting is conducted in conand passing the liquids'and` vapors between the various vstages in countercurr'ent fashion. Ali of this-will become apparent from the succeeding description .as will various other detailed but important features ofV my invention.

While it is obvious that my invention can be embodied in a great variety of forms, it will be described with particular reference to the accompanying drawings in which: Figure 1 is a ilow sheet of one form of my process illustrating one type of apparatus in accordance with my invention;

Figure 2 is an elevation partly in section of one of the contactors shown in Figure 1 together withv its associate agglomerator; and

Figure 3 vis a sectional plan taken along the line 3--3 of Figure 2.

Turning now to the drawings in more detail, well uids `from distillate well II can, if desired, be passed through cooler l2 into separator I3. This cooler can be so operated as to remove all or the bulk of the water 'presentlin the well fluids and this water can be removed from the bottom of separator I3 through valve I4 which is under the control of interfacial level controller I5. Liquid hydrocarbons existing as such in the reservoir or r precipitated in the progress of the well fluids up the well will also in general be recovered `in this separator and can be removed therefrom through valve I6 under the control of liquid level controller I1 and passed through line IB to storage tank I9. If the well uids are at very high pressure, the pressure can he reduced to some extent by means of pressure reduction valve 20 which is preferably locatedbetween cooler I2 and separator I3 as shown. A second pressure reduction valve ZI can be located in gas line 22 between separator I3 and the high pressure absorption system so that further pressure reduction with consequent temperature reduction can be eiiectuated before the high pressure absorption operation is carried out.

However, if the well fluids are not at an extremely high pressure, both of these pressure reduction valves can be omitted or left wide open -or in fact the well fluids can be passed directly v medium. This contactor together with the rest of the absorption system is operated at a pressure in excess of ,f 1200 pounds per square inch and preferably at considerably higher pressures as previously described. l v

As shown in 'Eigure 1, the absorption medium is introduced into the gas by means of carburetor 2l but'it will be-apparent that 'it'can be introduced into the gas in other manners or that the gas and absorption medium can be introduced separately at points near the bottom of the contactor in such manner as to disperse the absorber oil in the gas. IOne form of carburetor is shown in Figure 2. The'absorber oil enters through line 21 and the gas through line 22. The two are carburetted by means ,of nozzle 28 which is under` the control of adjusting screw 29.

The preferred type of contactor is best sho in Figure 2. This contactor is equipped with upwardly pointed annular baiiies 30. Any drainback liquid can be caught by these annular baiiies or vanes and from them overows into the ascending gas stream, thus causing the liquid to be resuspended in the gas phase. f

In general the upward velocity oflthe stream of mistimposed by the gas and suspended liquid Y- isgreat enough to prevent any appreciable drain back and/or collection of liquid in the bottom of the contactor. Such accumulation can, if necessary, be completely prevented by the provision of a throat 3| near the bottom of the contactor. Thisthroat tends to cause any back-draining liquid to be redispersed in the mist and to be carried upward and out of the contactor proper.

As the mist leaves contactor it passes upward through line 32 into agglomerator 33 (best seen in Figures 2 and 3) where provision is made for removal of the liquid from the mist and its collection and withdrawal through pipe 34. While the type of agglomerator shown is particularly advantageous other types of agglomerators, mist extractors, separators, etc. can be used. Centrifugal separation devices can aiso be used with particular advantage.

In the form of agglomerator shown, the upper end of pipe 32 (Figure 2) is packed with glass wool 35 and transforms the mistl containing very nely divided liquid particles into a mist of larger particles. -The upper. end of pipe 32 within agglomerator 33 is equipped with nozzles or jets 36 which direct the mist outwardly in a fanshaped spray along the wall of the agglomerator 33. On the wall of agglomerator 33 are numerous bailles 31 set at angles such that bailles are roughly parallel to the spray directed at them by jets 3E. This arrangement is appropriate for the co1- lection of the mist liquid.

The liquid thus collected drains into a circular collection trough 38 at the bottom of agglomerator 33 and thus out through pipe 34.

Turning once more to Figure 1, it will be seen that pipe 34 contains a liquid seal 39 which can suitably be in the form of a double reverse bend as shown. The purpose of this seal is to prevent the direct passage of gas between carburetor 26 and other points in the system through line 34 due to any pressure surges which might otherwise tend to blow the liquid from this line.

From liquid seal 38 the richor fat oil composed of the absorption medium and recovered distillate passes through line 40 to a suitable recovery and stabilization system of which one simplified form is shown.

Thus the rich oil can be .passed to a fractionating column 4| which can, if desired, be equipped with reboiler coil V42 and dephlemator 43 although these elements are not always necessary. This column is operated at a pressure somewhat lower than that of the absorption system and the pressure reduction is accomplished by reduction valve 44. Heat for the fractionation operation can be supplied to the incoming stream in part by the hot bottoms from tower 4| which are passed through heat exchanger 45 and in part by an extraneous heating fluid which is passed through heat exchanger 46.

Tower-4| is so operated that all gasoline range and lighter hydrocarbons pass overhead. If desired, the cut can be still higher, or, in other words, some kerosene range hydrocarbons can be taken overhead. This is notably desirable when a particularly high boiling absorber oil is used.

The bottoms from tower 4|, which may typically contain the complete heavier-than-gasoline cut can be, further fractionated if desired to isolate and return the preferred absorber oil, or the un. fractionated bottoms, to the high pressure ab sorption system through line 41, heat exchanger 45, cooler 48 and valved line 2lb by means of4 pump 49. Excess bottoms f rom.'fractionator 4| can be withdrawn from the system through valved line 50.

It will be apparentthat the absorber oil can be made up in whole or in part of the heavy ends of the distillate or a fraction thereof. On the other hand, it can advantageously be made up of a foreign material distilling above the distillation range of the distillate produced by my process, for instance, any conventional relatively high boiling absorber oil.

The overhead from fractionating tower 4I passes through condensing coil 5| to separator 52 in which gas and liquid phases are separated.

Condenser 5I is operated at such temperature as` to give practically complete condensation of normally liquid hydrocarbons together, if desired, with all or part of the butanes (or propane plus butanes) and the gases from the top of separator 52 can be passed to valved fuel line 53 as indicated or can be otherwise used, for instance by passing them through compressor 54 to high pressure line 55 where they join with residue gas from agglo merator 33h and are reintroduced by means of compressor 56 into the sub-surface reservoir from which the.well iluids were produced or into another sub-surface reservoir through input well 51.

The liquid phase from separator 52,*predominantly gasoline, can be reintroduced in part into the top of tower 4| as reflux by means of pump 58 and valved line 59 and vcan in part be introduced into a suitable stabilization ysystem (not shown) through valved line 60. Y

Returning now to the absorption system, it will be seen that I have described what is from the standpoint of the gas, the rst absorption stage, and from -the standpoint of the absorption oil,

the last absorption stage. This stage will here-v inafter be referred to as the first stage.

The gas from this first absorption stage passes through line 22a to a second carburetor 26a and thus into a second contactor 25a. In carburetor 26a. this gas meets absorber oil which has passed through the last stage of the absorption system. 'I'he gas and absorber oil pass upwardly through contactor 25a which can be equipped similarly to contactor 25 and thence to agglomerator 33a which can be equipped similarly to agglomerator 33. The liquid collected in agglomerator 33a passes out through pipe 34a to liquid seal 39a and ,thence through line 40a and carburetor 2liA into the flrstcontactor 25.

Gas from agglomerator 33a passes through line 22h to carburetor 2Gb wherein it meets lean oil introduced into the bottom of contactor 25h from fractionating column 4| through line 41, heat exchanger 45 and cooler 48 by means of pump 49.

Thus the fresh absorber oil having the maximum absorption capacity for the desired normally liquid hydrocarbons meets the gas which has had its content of normally liquid hydrocarbons reduced by two previous stages of ab-A sorption. In other words, the gas from which it is most dilcult to absorb further distillate hydropreviously been made. The liquid from this ag.

glomerator can pass out through line 34h and liquid seal 39h and thence through line 40h and carburetor 26a into the Ysecond contactor 25a.

Ultimately this absorber oil carrying distillate hydrocarbonsnds its way back to the first ab ture of my invention is to accomplish this with out the use of pumps. Due to inescapable pressure drops each succeeding contactor and .agglomerator is necessarily at a slightly lower pressure than the preceding one although the pressures in all contactors are preferably above the minimum to which reference has been made. 'Ihus in passing from the third stage to the second or from the second stage to the first the liquid phase, i. e. the absorber oil together with absorbed hydrocarbons, mustpass from a zone of relatively low pressure to a zone of higher pres,-

sure. In-the system shown this is accomplished without the use of pumps by virtue of the fact that the mists present in the contactors have average densities or average speciilc gravities lower than the densities or specic gravites oi the liquid phase material in the corresponding conduit running'from the agglomerator to the preceding contactor. Thus, for instance, the

pressure in agglomerator 33h is appreciably lower than the pressure in contactor 25a. Nevertheless, the head of liquid between agglomerator 33h and the inlet to contactor 25d is enough higher than the head of mist between this inlet and the top of agglomerator 33a so that the desired ilow is accomplished. This effect can,` if desired, be augmented by the action of the high pressure gas in aspirating the liquid into the carburetor. However, if the contactors and agglomerators are of proper design and sufficient height the desired iiow can beaccomplished without the use of such aspirating effect.

Any desired ratio of absorber oil to gas can be used, for instance, one to ten gallons per thousand cubic feet, for example four gallons per thousand cubic feet.'

The system shown has three stages but it will be apparent that a two stage system can be used.

However, I prefer ito use at least three stages and it is preferable to use a still higher number, for instance four or ve, depending on the economy balance between the improved recovery possible with additional stages as opposed to the increased capital cost of the added equipment.

Residue gas from agglomerator 33h passes out through line il and is preferably compressed at least in` large part for introduction into the subsurface reservoir from which the well iiuids were produced or into another sub-surface reservoir. This can be accomplished, for instance, by means of line 55, compressors 58 and input well 51.

As previously mentioned numerous modiilcations of my process and apparatus will occur to those skilled in the art in the'light of the :toregoing discussion and numerous improvements and details will be apparent. Thus for purposes of simplicity and to make the invention more readily comprehensible I have omitted various features of temperature, pressure and flow control` as well as other items familiar to those skilled in the art. Accordingly it is notany purpose to restrict my invention to the preferred modiiicaton illustrated but only to the scope oi the appended claim in which I have endeavored to define the novelty inherent in my invention.

I claim:

A device for contacting a gas concurrently with a liquid in mist form which comprises a vertically elongated contacting tower, inlet means for gas and liquid at the bottom of said tower, outlet means for gas and liquid at the top of said tower. a plurality of vertically spaced upwardly pointed annular bailies adjoined to said tower at their bottoms and adapted to form annular pools oi liquid at various elevations in said tower, whereby drain back liquidlis caught by said annular bailies and overiiows at the top of said bailes in intimate contact with the ascending stream of gas and liquid mist passing from said inlet means to said outlet means, thus causing said drain back liquid to be resuspended in said stream, and a-throat disposed below the lowermost of said baffles and above said inlet means,

whereby'any drain back liquid from said lower-l most baille is redispersed in the gas and liquid mist stream owing upward from said inlet means to said baffles.

. GEORGE S. BAYS. 

